均相多孔介質中運用二氧化碳置換法開採甲烷水合物的中尺度數值模擬研究

Mesoscale Numerical Simulation of exploiting Methane Hydrate by Carbon Dioxide Replacement in Homogeneous Porous Media

謝佩穎(Pei-Yin Hsieh)

指導教授 ： 施武陽

中原大學/工學院/環境工程學系/碩士(2019年)

https://doi.org/10.6840/cycu201900820

摘要

隨著經濟發展，全球暖化日益嚴重，傳統化石能源也即將用盡，各國的能源政策開始轉向低碳能源發展，由於天然氣水合物在全球中含量相當龐大，使得天然氣水合物開採研究備受關注，而近年來溫室效應越來越嚴重，如何減少二氧化碳的排放使溫室效應漸緩成為全球的議題，因此科學家們提出，利用二氧化碳置換甲烷水合物的方法，在置換過程中，不僅可以獲得新能源，同時可以將二氧化碳以水合物的狀態儲存於海底中。
本研究在不同甲烷與二氧化碳水合物平衡區域下，建立不同區域的甲烷水合物分解與二氧化碳水合物形成模型，利用CFD的三維非結構網格建立的動力學中尺度模型，透過堆積層代表體積元素方法呈現水合物動態變化的高精度模擬，利用有限體積法建立非結構網格系統，研究在高壓地層水流動條件下，二氧化碳置換甲烷水合物的過程，並且應用表面細切(Very Thin Layer)方法，分析水合物表面動量、濃度和熱的邊界層厚度，在不同邊界條件的溫度壓力下，進行動態模擬二氧化碳置換均質多孔介質甲烷水合物，以估算甲烷水合物分解與二氧化碳水合物形成的速率以及溫度變化。
透過本研究可以得知，在甲烷水合物穩定區與不穩定區置換時，甲烷水合物分解與二氧化碳水合物形成的濃度與溫度動態變化，並了解在理想的假設情況的隨時間反應的置換過程發生的變化。

關鍵字

天然氣水合物分解 ； 二氧化碳置換 ； 計算流體力學 ； 均相多孔介質

並列摘要

With the development of the economy, global warming is becoming more and more serious, traditional fossil energy will be exhausted, and the energy policies of various are beginning to lead to low-carbon energy development. Due to the huge content of natural gas hydrates in the world, research on natural gas hydrate mining has attracted much attention. In recent years, the greenhouse effect has become more and more serious. How to reduce carbon dioxide emissions has made the greenhouse effect gradually become a global issue. Therefore, scientists have proposed that carbon dioxide can be used to replace methane hydrate, and not only new energy can be obtained in the replacement process, but also carbon dioxide can be stored in the deep ocean in the form of a hydrate.
In this study, methane hydrate dissociation and CO2 hydrate formation models were established under different methane and carbon dioxide hydrate equilibrium regions. Using the dynamic mesoscale model established by the three-dimensional unstructured mesh of CFD technology, to present high-precision simulation of sediment dynamics by Representative elementary volume(REV) method. The finite volume method is used to establish an unstructured grid system, and the process of CO2 replacement of methane hydrate under water flow conditions was studied, and applying the VTL (Very Thin Layer) method to calculate the hydrate surface momentum, concentration, and thermal boundary layer thickness. Under the temperature and pressure of different boundary conditions, the dynamic simulation of CO2 was used to replace the homogeneous porous medium methane hydrate, and the rate of methane hydrate dissociation and CO2 formation and temperature change were estimated.
Through this study, it can be seen that when the methane hydrate replaces in the stable or unstable region, the concentration and temperature of methane hydrate dissociation and CO2 hydrate formation change dynamically, and understand the changes in the replacement process over time in the ideal hypothetical situation.

並列關鍵字

gas hydrate dissociation ； carbon dioxide replacement ； computational fluid dynamics ； homogeneous porous media

參考文獻

Agency, I.E., 2018. World Energy Outlook 2018.

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